Ignition distributors



W. H. COOKSEY May 5, 1970 IGNITION DISTRIBUTORS 2 SheetsSheet 1 FiledMarch '7, 1968 INVE NTOR ATTORNEYS May 5, 1970 COOKSEY 3,510,609

IGNITION DISTRIBUTORS Filed March '7. 1968 2 Sheets-Sheet 2 INVENTORATTQRNEYS United States Patent 3,510,609 IGNITION DISTRIBUTORS WilliamHarold Cooksey, Walsall, England, assignor to Joseph Lucas (Industries)Limited, Birmingham, Eng- US. Cl. 200-19 2 Claims ABSTRACT OF THEDISCLOSURE A distributor includes a casing, having a cam shaft mountedfor rotation therein, the cam shaft carrying the rotor arm of thedistributor. A fixing plate is secured within the casing and acorrection plate is supported within the casing for movementsubstantially radially with respect to said cam shaft. A timing plate isengaged for the correction plate for movement angularly relativethereto, and the contact breaker assembly of the distributor is mountedon the timing plate. Movement of the correction plate serves to move thecontact breaker assembly, through the timing plate, towards or away fromthe shaft so as to adjust the operating gap of the contacts of thecontact breaker assembly, and the arrangement is such that at a givensetting of said operating gap the correction plate constrains the timingplate to move relative to the cam shaft in a path such that saidoperating gap remains constant.

This invention relates to ignition distributors.

A distributor according to the invention includes a casing, a cam shaftrotatable within the casing and carrying the rotor arm of thedistributor, a fixing plate secured within the casing, a correctionplate movable substantially radially with respect to said shaft and atiming plate engaged with the correction plate for movement angularlyrelative thereto and carrying the contact breaker assembly of thedistributor, movement of the correction plate moving the contact breakerassembly through the timing plate towards or away from the shaft toadjust the operating gap of the contacts of the contact breaker assemblyand the arrangement being such that at a given setting of said gap thecorrection plate constrains the timing plate to move relative to the camshaft in a path such that said operating gap remains constant.

One example of the invention is illustrated in the accompanying drawingswherein FIG. 1 is a part sectional plan view of an ignition distributorwith parts thereof omitted for clarity and,

FIG. 2 is an exploded perspective view, of part of the distributor shownin FIG. 1.

Referring to the drawings the distributor includes a hollow cylindricalcasing having secured therein an annular fixing plate 11. The cam shaft10a of the distributor extends axialiy through the central hole of theplate .11 and is journalled for rotation in the casing 10. Arranged onthe lower surface of the plate 11 and pivotally engaged therewith is agenerally rectangular adjusting plate 12. The plate 11 and the plate 12are pivotally interconnected by a pin 13 which extends through one endof the plate 12. The plate 12 carries an upstanding post 14 near its midpoint, the post 14 extending upwardly through a slot 15 in the plate 11.At its end remote from the post 13 the plate 12 is formed with anupstanding lug 16 provided with a screw-threaded hole 18, the lug 16extending through a further slot 17 in the plate 11. A screw 19 extendsthrough a clearance hole in the casing of the distributor and is engagedwith the lug 16 so that rotation of the screw 19 causes pivotal movementof the plate 12 with respect to ice the plate 11. A spring 21 isinterposed between the casing of the distributor and the lug 1-6 andsurrounds the screw 19, the spring 21 serving to take up backlashbetween the screw-threads of the screw 19 and the lug 16.

Diametrically opposite the post 14 but supported on the plate 11 is ashort upstanding post 22. Engaged with the posts 14, 22 and in contactwith the upper surface of the plate 11 is an annular correction plate23, the post 14 extending through a hole in the plate 23 while the post22 is received in a generally radial slot 24 in the plate 23. The plate23 has formed therein an arcuate slot 25 ad jacent the slot 24, and inone position of the plate 23 relative to the cam shaft of thedistributor, the centre of curvature of the slot 25 lies between thepost 14 and the axis of the cam shaft, and on an imaginary line passingthrough the axis of the post 14 and the axis of the cam shaft.

Slidably supported on the plate 23 is an annular timing plate 26. Theplate 26 is formed with a radially extending slot 27 through which thepost 14 extends and supported on the plate 26 for actuation by the camshaft of the distributor is a contact breaker assembly 28. Extendingdownwardly from the plate 26 is a pin 29 which passes through a hole inthe push rod 31 of a conventional vacuum advance unit (not shown). Thefree end of the pin 29 engages in the arcuate slot 25 in the plate 23.The upper end of the post 14 is screw-threaded and receives a nut 32 anda washer 33, a spring 34 being trapped between the washer 33 and theplate 26 and urging the plate 26 towards the plate 23. The plate 26 isprovided with a plurality of nylon pips 35 which engage the plate 23 andsupport the plate 26 for sliding movement thereon.

In use the ignition timing of the distributor is dependent on theangular position of the contact breaker assembly 28 with respect to thecam shaft of the distributor and the operating gap of the contactbreaker assembly 28 is dependent on the position of the assembly 28radially with respect to the cam shaft of the distributor. Thus it willbe appreciated that unless the contact breaker assembly 28 is movedabout an arc struck from the axis of the shaft, then when the vacuumadvance unit operates the operating gap of the assembly 28 will changeas the ignition timing is varied.

The curvature of the slot is so calculated that when the operating gapof the assembly is correct, movement of the push rod 31 will move theplate 26 and consequently the assembly 28 through the pin 29, along anarc struck from the axis of the shaft and the operating gap of theassembly 28 will therefore remain constant.

It will be appreciated that the consequential movement of the plate 26with respect to the post 14 is permitted by the engagement of the post14 in the slot 27.

In order to adjust the operating gap of the assembly 28 to its optimumvalue, the screw 19 is rotated. As the screw 19 is rotated, the plate 12is caused to pivot about the post 13 so moving the post 14 toward oraway from the cam shaft of the distributor. As the post 14 moves, itcarries the plate 23 with it, and by virtue of the engagement of the pin29 in the slot 25 the plate 26 moves with the plate 23. Thus theassembly 28 is moved towards or away from the cam shaft of thedistirbutor thereby adjusting the operating gap of the assembly 28.

The distributor is particularly useful where the vacuum advance unit ismodified to give a large degree of ignition retard at certain conditionsof the engine with which it is employed, since this arrangement requireda large angular movement of the timing plate 26.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

1. An ignition distributor including a casing, a cam shaft, meansmounting the cam shaft for rotation Within the casing, a rotor arm ofthe distributor carried by the cam shaft, a fixing plate secured withinthe casing, a correction plate mounted for movement substantiallyradially with respect to the cam shaft, a timing plate engaged with thecorrection plate, the timing plate being movable angularly relative tothe correction plate, and a contact breaker assembly carried by thetiming plate, one of the pair of plates constituted by the timing plateand the correction plate being formed with an arcuate slot, and theother of said pair of plates carrying a post which rides in said arcuateslot, and the arrangement being such that movement of said correctionplate substantially radially with respect to the cam shaft moves thetiming plate, and therefore the contact breaker assembly towards or awayfrom the cam shaft, so that the operating gap of the contact of thecontact breaker assembly is adjusted, and, at a given setting of theoperating gap of the contacts of the contact breaker assembly, thecentre of curvature of said arcuate slit lies on the axis of the camshaft, so that the timing plate is constrained, by the action of saidpost in said arcuate slot, to move angularly with respect to thecorrection plate about the axis of the cam References Cited UNITEDSTATES PATENTS 2,769,047 10/ 1956 Hartzell et a1. 200-31 2,835,7555/1958 Filko 20031 XR 2,923,785 2/ 1960 Longenec-ker 200-31 3,242,274 3/1966 Sanden 20031 ROBERT K. SCHAEFER, Primary Examiner J. R. SCOTT,Assistant Examiner

